Printed electrical circuits



July 5, 1960 LENQ ETAL PRINTED ELECTRICAL CIRCUITS 2 Sheets-She et 1Filed Dec. 10, 1954 A Home y July 5,1960 J A LENO ETQAL 2,943,966PRINTED ELECTRICAL CIRCUITS Filed Dec. 10, 1954 2 Sheets-Sheet 2 FIGS.

Inventor: J. A. LENO- A. M. SEARLE A ttorn e y PRINTED ELECTRICALCIRCUITS John Albert Leno and Arthur Mackenzie Searl'e, London,

England, assignors to International Standard Electric Corporation, NewYork, N.Y.

Filed Dec. 10, 1954, $81. No. 474,566

Claims priority, application Great Britain Dec. 30, 1953 1 Claim. (Cl.154-80) This invention relates to improved methods for making inductivewindings for electrical apparatus.

Methods for producing what are commonly called printed circuits are wellknown and comprise forming conductive tracks upon an insulating surfacesuch as by printing with, say, a conducting printing ink orelectroplating or otherwise depositing the tracks upon the surface of aninsulating carrier.

It is known from British Patent No. 639,591, to provide a carrier havinga plurality of uniplanar turns of conducting track thereon which form aninductive winding.

The main feature of the present invention is a method of producing aninductive electrical winding which comprises printing or otherwisedepositing a continuous conductive track on one surface of a fiatinsulating carrier and folding the carrier through substantially 180along a line crossed by the track whereby portions of the track on thecarrier on each side of the line are brought into relative positionabout an axis at right angles to the surface of the carrier to form oneturn of the winding.

The invention will be particularly described with reference to theaccompanying drawings illustrating various embodiments.

In the drawings:

Fig. 1 illustrates in plan view a conducting track on an insulatingcarrier;

Fig. 2 is a perspective view of the carrier in Fig. 1 during folding;

Fig. 3 is a plan view of the carrier after folding has been completed;

Fig. 4 illustrates in plan view another embodiment having a moreelaborate conducting track;

Figs. 5 and 6 are perspective views of the carrier in Fig. 5 atdifferent stages of folding;

Fig. 7 is a plan view after folding has been completed;

Fig. 8 illustrates in plan view a further embodiment having a trackcomprising a plurality of loops or turns and Fig. 9 shows in perspectivehow a number of carriers may be folded together ot provide atransformer.

Referring first to Fig. 1 it will be seen that an insulating carrier, inthe form of a piece of paper or fabric 1, which may have beenimpregnated with an insulating resin, has printed or otherwise depositedupon it in wellknown manner a conducting track 2 which may comprisesilver or other metallic paste.

The carrier may be regarded as comprising a number of substantiallyequal sections or areas 3, 4, 5, 6 bounded by imaginary lines 7, 8, 9,shown dotted, along which the carrier will presently be folded. Theshape of the track is such that, on each of the sections 3, 4, 5, 6,there is a portion 10, 1'1, 12 or 13, so shaped that when, for example,the carrier is folded through 180 along line 7 the portions 10, 11, onsections 3 and 4 combine, in plan, to form a substantially enclosedfigure, such as a circle. Thus, when the carrier 1, is folded fan-wiseabout lines 7, 8, 9, as shown in Fig. 2, the portions 12,

2,943,966 Patented July 5, 1960 'ice' 13, on sections 5, 6 form asubstantially complete turn as shown in Fig. 3 and, likewise, theportions 10, 1 1, on sections 3, 4 form another substantially completeturn immediately behind, the various portions being arranged to meettheir neighboring portions at. the folding lines -i {7,-8, 9, or to bejoined together as shown in Fig. 1 by means of short track lines 14. Thetrack 2 may be terminated as shown by areas 15 to act as terminals. Itwill beappreciated that some means (not shown) of preventing contactbetween the track portions on adjacent jsections will be necessany, whenfolding takes place. Such means maybe by printing with'an insulatingmaterial or by interleaving, as will be explained in connection withFig. 9.

The winding, as shown in Fig. 3 and which may have a hole therethroughfor a core, may be suitably consolidated by heat and pressure in knownmanner. It will be understod that while the carrier 1 has been showndivided into only four sections 3, 4, 5, 6, thereby producing only atwo-turn winding, it may be as long as desirable and be divided into anydesired number of sec tions, bearing in mind that an even number ofsections enables both the terminals 15 to appear on the outside faces ofthe winding.

In order that the carrier 1 shall not be unduly long, the track may bearranged as a substantially complete loop or turn as shown in Fig. 4. Inthis case the carrier 16 is arranged to be folded first along a centreline 17 as shown in Fig. 5 and then in fanwise or other fashion alonglines 18, 19, 20, as shown, for example, in Fig. 6. The configuration ofthe track is such that portions 21, 22, ultimately form one turn, 23 and24 another turn, and so on. Thus the track shown in Fig. 4 forms awinding having four turns when folded as in Figs. 5, 6, 7, the terminalareas 25, being conveniently arranged side by side at one end of thewinding.

A considerably larger number of turns can be provided withoutappreciable increase in the size of the insulating carrier by arrangingthe track as shown in Fig. 8. In this case the track comprises a numberof loops or turns arranged one within the next in spiral form.

In Fig. 8 the track is of the same general configuration as in Fig. 4,but consists of five loops or turns, 26, 27, 28, 29, 30, substantiallyequidistant one from the next. It will be obvious that when folded alongthe centre line 17, the portions 31, 3-2, 33, 35 together with therespective portions 36, 37, 38, 39, 40, each form complete turns andthat when folded fanwise as already explained there are produced fivetimes as many turns as were provided from the track in Fig. 4, that isto say, the track shown in Fig. 8 provides a coil having twenty turns.

Fig. 9 shows how two carriers, having tracks thereon as in Fig. 8, maybe folded together so that the two windings have a substantially commonaxis and are thereby inductively coupled as in a transformer.

The two carriers which are here designated 31, 32 are insulated from oneanother by means of an insulating foil or blank carrier 33, shownshaded. Other insulating foils (not shrown) or extensions of the foil33, may be inserted where required to prevent undesired contact betweenportions of the track on each of the carriers 31, 32. By suitablearrangement of the carriers 31, 32, the terminals of each of thewindings may be arranged to appear on an outside face of thetransformer.

-It will be clear to those skilled in the art that various methods ofinterleaving or folding together of carriers may be employed and thatthe insulating material used may be plastic material equally well asresin-impregnated paper or fabric.

Furthermore the carriers 31, 32 may be replaced by a.

single carrierhaving the two tracks comprising the two windings printedone on each side thereof.

While the principles of the invention have been described above inconnection with specific embodiments,

and particular modifications thereof, it is tube -clearly" understoodthat this: description is .madeonly by :way of Y exampleand not asalimit-ationon-thescope of the in vention.-

What ,we claim is:

An inductive electrical winding; comprising an -insu1at ing carrierhaving portions folded back-against each other,

thus forming aplurality of parallel surfaces, a printed circuit oncertain of said surfaces, each- 0f saidprintedcircuits havin theconfiguration of portions only -of a plurality of complete turnsabout anaxis perpendicular to said surfaces and cooperatingwith correspondingturn portions on another one of said surfaces to form a correspondingplurality of complete turns, said cooperating dicular to. each other,the printed circuits being arranged so that :both ends of the continuousconductor formed thereby are on the same portion of said carrier.

References Cited-in. the-file of this patent UNITED STATES PATENTS 5

